Which tissue property leads to posterior enhancement behind a structure?

• A. High attenuation
• B. Medium attenuation
• C. Low attenuation
• D. Very high attenuation

Answer: (C)

Posterior enhancement occurs when the tissue behind a structure attenuates less energy than surrounding tissue. When the beam passes through a low-attenuation medium (such as a fluid-filled cyst), most of the ultrasound energy is transmitted with little loss. More sound energy then reaches deeper tissues and returns as stronger echoes, making the area behind the structure appear brighter. If attenuation were high or very high, the beam would lose more energy before it reaches deeper tissues, leading to darker areas behind the object (posterior shadowing). Moderate attenuation would not produce as pronounced an effect. Therefore, low attenuation is the property that leads to posterior enhancement.